1. Field of the Invention
The present invention relates to the drying of water-containing hydrocarbons, notably those hydrocarbons used in the production of chloromethanes.
This invention especially relates to the drying of optionally halogenated hydrocarbons which contain both water and hydrochloric acid.
2. Description of the Prior Art
The drying of perchloroethylene using a solution of calcium chloride (Chem. Abstracts, Vol. 99,177849d) and in the absence of hydrochloric acid is known to this art. The drying of chloroform CHCl.sub.3 and carbon tetrachloride CCl.sub.4, after purification thereof by extraction with water (Chem. Abstracts, Vol. 62,2227e), with calcium chloride (CaCl.sub.2), but always in the absence of hydrochloric acid, is also known to this art.
Nonetheless, serious need exists in this art for a technique to dry hydrocarbons containing hydrochloric acid and water without concomitantly removing the hydrochloric acid. This problem is particularly acute in the synthesis of chloromethanes as they exit the chlorination reactor, where the chloromethanes are mixed with hydrochloric acid (in each instance that a hydrogen atom is substituted by a chlorine atom, one mole of hydrochloric acid is formed as a by-product) and with water which is introduced into the process as an impurity in the starting materials. In such process the water must be removed to prevent its accumulation and also to avoid clogging or blocking the pipelines with ice and hydrates. The hydrochloric acid is recovered and is then reclaimed by conversion into chlorine in a Deacon reaction or an oxychlorination reaction. If water is removed from this mixture of chloromethanes by condensation, then there is a risk, due to the great solubility of hydrochloric acid in water, of producing a solution of hydrochloric acid in water which is subsequently difficult to separate There is a risk that the disadvantage will be the same if it is desired to separate the water from this mixture using a drying agent.
Surprisingly, it has now unexpectedly been determined that hydrocarbons containing hydrochloric acid and water can be selectively dried, while retaining only water on the drying agent.